Frost heave and thaw weakening can cause damage to pavement structures, such as parking areas, roadways, airfields, etc., in northern regions. The formation of ice lenses in the pavement structure is a significant contributor to such damage, as illustrated in FIG. 1. Three elements are necessary for ice lenses, and thus frost heave, to form. These are: (1) frost susceptible soil, (2) subfreezing temperatures, and (3) water. Often, water is available from the groundwater table, infiltration, an aquifer, or held within the voids of fine-grained soil. By removing any of the three elements above, frost heave and thaw weakening can be at least minimized or eliminated altogether.
Techniques have been developed to mitigate the damage to pavement structures caused by frost heave and thaw weakening. One such method involves removing the frost susceptible soils and replacing them with non-frost susceptible soils. The non-frost susceptible soil is placed at an adequate thickness to reduce the strain in the frost-susceptible soil layers below to an acceptable level. Other methods include use of insulation to reduce the freeze and thaw depth. In areas where removal of frost susceptible soils and reduction of subfreezing temperature are difficult and expensive, removal of water can lead to savings in construction costs by reducing the formation of ice lenses. By breaking the capillary flow path, frost action can be less severe.
A capillary barrier is a layer of coarse-grained soils or geosynthetic in a fine grained soil that (i) reduces upward capillary flow of soil water due to suction gradient generated by evaporation or freezing, and (or) (ii) reduces or prevents water from infiltrating from the overlying fine-pored unsaturated soil into the soil below the capillary barrier. In the latter case, if the capillary barrier is sloped, the infiltrating water flows in the fine soil downwards along the interface with the capillary barrier. Geosynthetic drainage nets (geonets) have been found to serve as capillary barriers because of their large pore sizes. The performance of nonwoven geotextiles as a capillary barrier appears to be compromised by soil intrusion into their interiors, decreasing the pore size and increasing the affinity of the material to water. Further, as reported by Henry (1998), “The use of geosynthetics to mitigate frost heave in soils.” Ph.D. dissertation, Civil Engineering Department, University of Washington, Seattle, hydrophobic geotextiles have been more effective in reducing frost heave than hydrophilic geotextiles.
The above mentioned capillary barriers attempt to cut off the capillary water flow by generating a horizontal layer with very low unsaturated permeability under suction. The whole structure is permeable for downward rainfall infiltration. This type of capillary barrier requires that the barrier thickness exceed the height of the capillary rise of water in them. In addition, it provides conditions suitable for water vapor flow because of their high porosity and comparatively low equilibrium degrees of saturation.
Thus, there remains a need for a woven geosynthetic fabric with differential wicking capability that reduces or eliminates frost heave in soils. Accordingly, it is to solving this and other needs that the present invention is directed.